[EN] The combination of different materials to form a single structural member to take profit of their individual good characteristics is a successfully established practice in building industry. In concrete filled tubular columns (CFT) the combined action of steel and concrete results in many positive attributes at ambient temperature: high load-bearing capacity with smaller cross-section size, aesthetics, high stiffness and ductility and reduced construction cost. In the last decades, the use of CFT columns in building industry, especially in high-rise buildings, has increased not only because of their positive characteristics at room temperature, but also for their inherent high fire resistance. Besides, CFT sections are greatly versatile given that they admit different types of concrete infill such as plain concrete, bar-reinforced concrete or fiber reinforced concrete; and also a wide variety of shapes. Although the more commonly used shapes are circular, and rectangular, new configurations and shapes are continuously appearing together with innovative materials. The ambient temperature behavior of CFT columns has been deeply studied and, in turn, the investigations dealing with their fire behavior have increased. For its structural analysis, the column can be considered as an isolated member or as a column integrated in a structure interacting with other structural members. The review of the state of the art in the area of CFT columns in fire carried out in the framework of this thesis has pointed out that most works cover the fire response of isolated members and that the existing studies on columns within frames differ in their proposals and conclusions. In this thesis, the fire response of CFT columns is analyzed by means of a fiber beam element model. First, a realistic cross-sectional thermal model is implemented to be integrated in the thermo-mechanical model developed whose accuracy is validated against experimental results after its calibration. Parametric studies are carried out with the aim of investigating the main factors affecting the problem and developing a simple calculation method based on Eurocode 4 and using the concept of equivalent concrete core cross-section. Finally, given the reduced computational cost of the fiber model, the effects of axial and rotational restraint in the fire response of CFT columns are investigated by integrating the heated CFT column within a frame. A parametric analysis is performed in order to draw conclusions about this interaction and contrast the current code provisions. The scope of this thesis is limited to circular CFT columns subjected to concentric axial loads. / [ES] Combinar diferentes materiales en un único elemento estructural para aprovechar las fortalezas individuales de cada uno es una práctica consolidada con éxito en el sector de la construcción. En los pilares tubulares de acero rellenos de hormigón (CFT) la acción conjunta del acero y el hormigón presenta muy buenas cualidades a temperatura ambiente: alta capacidad de carga con secciones pequeñas, buena apariencia, alta rigidez y ductilidad y bajo coste de puesta en obra. En las últimas décadas, el uso de pilares CFT en el sector de la construcción, especialmente en edificios de gran altura, ha aumentado no solo debido a sus buenas características a temperatura ambiente sino también por su inherente alta resistencia al fuego. Además, las secciones de pilares CFT son muy versátiles ya que admiten diferentes tipos de relleno, como hormigón en masa, con armaduras o reforzado con fibras; y también una amplia variedad de formas. Aunque los perfiles tubulares más usados son los circulares y rectangulares, nuevas configuraciones están continuamente en desarrollo junto con nuevos materiales. El comportamiento de los pilares CFT a temperatura ambiente ha sido ampliamente estudiado y, a su vez, las investigaciones sobre su comportamiento a fuego han aumentado. Para su análisis estructural, el pilar puede ser considerado como un elemento aislado o como un elemento integrado en una estructura que interactúa con otros elementos estructurales. La revisión del estado del arte en el área de los pilares CFT sometidos a fuego llevado a cabo en el marco de esta tesis ha puesto de manifiesto que la mayoría de los trabajos cubren la respuesta a fuego de elementos aislados y que los estudios existentes sobre pilares en estructuras difieren en sus propuestas y conclusiones. En esta tesis, la respuesta a fuego de pilares CFT se analiza por medio de un modelo de elementos viga con integración por fibras. En primer lugar, se implementa un modelo térmico realista para ser integrado en el modelo termo-mecánico desarrollado cuya precisión se valida con resultados experimentales después de ser calibrado. Un estudio paramétrico se lleva a cabo con el objeto de estudiar los principales factores que afectan al problema y desarrollar un modelo simplificado de cálculo basado en el Eurocódigo 4 Parte 1-1 y que emplea el concepto de sección equivalente del núcleo de hormigón. Finalmente, dado el reducido coste computacional del modelo de fibras, se investigan los efectos de la restricción axial y rotacional en la respuesta frente al fuego de los pilares CFT integrando la columna expuesta a fuego dentro de una subestructura. Se ejecuta un estudio paramétrico para extraer conclusiones sobre esta interacción y contrastar las prescripciones de la normativa actual. El alcance de esta tesis queda limitado a pilares CFT sin protección externa, de sección circular y sometidos a carga axial centrada. / [CA] Combinar distints materials en un únic membre estructural per a aprofitar les fortaleses individuals de cada u és una pràctica consolidada amb èxit en el sector de la construcció. En els pilars tubulars d'acer omplerts de formigó (CFT) l'acció conjunta de l'acer i el formigó presenta molt bones qualitats a temperatura ambient: alta capacitat de càrrega amb seccions xicotetes, bona aparença, alta rigidesa i ductilitat i baix cost de posada en obra. En les últimes dècades, l'ús de pilars CFT en el sector de la construcció, especialment en edificis de gran altura, ha augmentat no sols degut a les seues bones característiques a temperatura ambient, sinó també per la seua inherent alta resistència al foc. A més, les seccions de pilars CFT són molt versàtils, doncs admeten distints tipus de farcit, com formigó en massa, amb armadures o reforçat amb fibres; i també una àmplia varietat de formes. Encara que els perfils tubulars més usats són els circulars i rectangulars, noves configuracions estan contínuament en desenvolupament junt amb nous materials. El comportament dels pilars CFT a temperatura ambient ha sigut àmpliament estudiat i, al mateix temps, les investigacions sobre el seu comportament a foc han augmentat. Per a la seua anàlisi estructural, el pilar pot ser considerat com un element aïllat o com un element integrat en una estructura que interactua amb altres elements estructurals. La revisió de l'estat de l'art en l'àrea dels pilars CFT sotmesos a foc, duta a terme en el marc d'aquesta tesi, ha posat de manifest que la majoria dels treballs cobreixen la resposta a foc d'elements aïllats, i que els estudis existents sobre pilars en estructures difereixen en les seues propostes i conclusions. En aquesta tesi, la resposta a foc de pilars CFT s'analitza mitjançant un model d'elements biga amb integració per fibres. En primer lloc, s'implementa un model tèrmic realista per a ser integrat en el model termo-mecànic desenvolupat, i la seua precisió es valida amb resultats experimentals desprès de ser calibrat. Un estudi paramètric es du a terme amb l'objectiu d'estudiar els principals factors que afecten al problema i desenvolupar un model simplificat de càlcul basat en l'Eurocodi 4, Part 1-1 i que empra el concepte de secció equivalent del nucli de formigó. Finalment, tenint en compte el reduït cost computacional del model de fibres, s'investiguen els efectes de les restriccions axial i rotacional en la resposta a foc dels pilars CFT integrant la columna exposada a foc dins d'una subestructura. Un estudi paramètric s'executa per a obtenir conclusions sobre aquesta interacció i contrastar les prescripcions de la normativa actual. L'abast d'aquesta tesi queda limitat a pilars CFT sense protecció externa, de secció circular i sotmesos a càrrega axial centrada. / Ibáñez Usach, C. (2016). FIRE RESPONSE ANALYSIS OF CIRCULAR CONCRETE FILLED TUBULAR COLUMNS AND THE EFFECTS OF AXIAL AND ROTATIONAL RESTRAINTS [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/60150 / Premios Extraordinarios de tesis doctorales

Yes / This paper presents the results of a numerical investigation on strategies for enhancing the fire behaviour of concrete-filled steel tubular (CFST) columns by using inner steel profiles such as circular hollow sections (CHS), HEB profiles or embedded steel core profiles. A three-dimensional finite element model is developed for that purpose, which is capable for representing the various types of sections studied and the nonlinear behaviour of the materials at elevated temperatures. High strength steel is considered in the numerical model, as a possible way to lengthen the fire endurance. The numerical model is validated against experimental results available in the literature for various types of steel-concrete composite sections using inner steel profiles, obtaining satisfactory results. Based on the developed numerical model, parametric studies are conducted for investigating the influence of the cross-sectional geometry and the steel grade of the inner profiles on the fire performance of these composite columns, for eventually providing some practical recommendations.

Im Rahmen experimenteller Untersuchungen wurden Stahlbetonplatten hergestellt, mit verschiedenen textilen Bewehrungen verstärkt, mit 125 % Gebrauchslast vorgeschädigt und anschließend unter Gebrauchslast mit einer Brandbelastung nach der Einheitstemperaturkurve (ISO-834, Cellulosic curve) beaufschlagt. Alle Platten hielten der Brandbelastung bei gleichzeitiger Biegebeanspruchung mehr als 60 Minuten stand und zeigten weder Betonabplatzungen noch andere optische Schädigungen auf. Die für dieses überraschend positive Ergebnis verantwortlichen Mechanismen werden diskutiert, sind aber noch nicht vollständig verstanden. Eine Schlüsselrolle spielt dabei vermutlich das gute Rissverhalten von Textilbeton und interne Umlagerungen zwischen Textil und Stahlbewehrung.

La Nouvelle-Calédonie qui présente une biodiversité à la fois exceptionnelle et très menacée, fait partie des points chauds de biodiversités définis à l'échelle globale comme zones prioritaires pour la conservation. Les incendies, d'origines anthropiques et constituant l'une des principales menaces pesant sur les écosystèmes naturels néo-calédoniens, conduisent à un recul des forêts denses humides (forêts par la suite) principalement au profit des savanes sur substrats volcano-sedimentaires. Au cours de cette thèse, les processus écologiques mis en jeu dans les dynamiques des forêts et des savanes, liés aux variations du régime d'incendie, ont été étudiés à différentes échelles spatiales et temporelles. L'analyse de la distribution spatio-temporelle des forêts et des savanes à l'échelle du paysage a mis en évidence différents facteurs dirigeant la dynamique paysagères et identifié des zones de recolonisation forestière. Différents modèles de succession secondaire et cortèges d'espèces pionnières ont été identifiés à partir de l'analyse de ces zones de recolonisation. La mesure de traits fonctionnels et l'utilisation de modèles semi-physiques de dommages causés par les incendies ont révélé une faible tolérance aux incendies de ces espèces. Enfin, une analyse multivariée de la structure, de la composition floristique et des conditions micro-climatiques des zones clés de transitions entre la savane et la forêt a permis de mieux comprendre les processus d'expansion et de contraction forestière. / New Caledonia, which presents both an exceptional and highly endangered biodiversity, is one of the worldwide biodiversity hotspots for conservation priority. Human-induced fires, which are one of the main threats to natural ecosystems in New Caledonia, lead to the expansion of savannas on volcano-sedimentary substrates at the expense of rainforests. In this thesis, the ecological processes, which are involved in the dynamics of rainforests and savannas and related to changes in fire regime, have been studied at different spatial and temporal scales. The analysis of the spatio-temporal distribution of rainforests and savannas across the landscape allowed us to both point-out the different drivers of their dynamics and to identify areas of rainforest recolonization. Different secondary succession patterns and pioneer species assemblages were identified from the analysis of these areas of recolonization. The analysis of measured functional traits and the use of semi-physical models of fire-caused damages highlighted the low tolerance of these pioneer species to fire. Finally, a multivariate analysis of the structure, the floristic composition and the micro-climatic conditions of transitional zones between savanna and rainforest, has allowed us to better understand the processes of rainforest's expansion and contraction. This thesis opens a new field of research in New Caledonia with important implications in rainforest's restoration and sustainable management.

Le présent travail propose et développe une méthode originale de dimensionnement vis-à-vis de l'incendie de parois de bâtiments industriels, en s'intéressant plus spécifiquement au cas des panneaux en béton armé de grande hauteur. Soumis à un fort gradient thermique, ces derniers subissent en effet des déplacements hors plan importants qui, du fait de l'excentrement du poids propre qui en résulte, vont engendrer des efforts de flexion venant s'ajouter aux efforts de compression déjà existants. Un tel changement de géométrie, d'autant plus prononcé que le panneau est de grande hauteur, combiné à une dégradation simultanée des propriétés de résistance des matériaux sous l'effet de l'élévation de température, peut conduire à un effondrement de la structure sous poids propre, bien avant par exemple l'apparition d'une instabilité de type flambement. L'approche proposée repose très largement sur la théorie du Calcul à la Rupture, appliquée d'une part à la détermination d'un diagramme d'interaction au feu caractérisant la résistance du panneau en chacune de ses sections, d'autre part à l'analyse de la ruine globale du panneau dans sa configuration déformée. Cette démarche est d'abord mise en œuvre et complètement explicitée dans le cas où le panneau peut être modélisé comme une poutre unidimensionnelle, conduisant à la détermination exacte d'un facteur adimensionnel caractérisant la stabilité de ce dernier. La généralisation de la méthode de calcul à la configuration plus réaliste, mais plus complexe, d'un panneau schématisé comme une plaque rectangulaire, est ensuite développée. Elle aboutit à un certain nombre de résultats préliminaires qui devront être confortés et affinés dans un travail ultérieur. L'approche théorique ici présentée est par ailleurs complétée par un volet expérimental (essais de flexion quatre points de dalles dans un four à maquette) qui a permis de valider au moins partiellement les évaluations du diagramme d'interaction prédites par le calcul / In this contribution, an original and comprehensive method aimed at designing vertical concrete walls submitted to fire loadings, is proposed and developed, with a special emphasis on high rise panels used in industrial buildings. Indeed, when subjected to high thermal gradients, such slender structures exhibit quite significant out-of-plane movements, resulting in an eccentricity of the gravity loads and thus to bending moments in addition to the pre-existing compressive forces. It is such a change of geometry, which is all the more pronounced as the panel is tall, combined with a temperature-induced degradation of the constituent materials strength properties, which may explain why an overall collapse of the structure may occur, well prior to buckling instability. The proposed approach is fundamentally based on the theory of yield design. This theory is first applied to the determination of an interaction diagram, characterizing the fire resistance of a reinforced concrete panel cross-section. It is then implemented as a design method for analysing the stability of the panel in its previously calculated deformed configuration. The whole procedure is explained in full details in the simplified situation when the high rise panel can be modeled as a one-dimensional beam, leading to the exact determination of a dimensionless factor characterizing the stability of the panel. The method is then extended to deal with a more realistic, but somewhat more complex, configuration of a rectangular panel. Some preliminary results, which need to be further validated in a subsequent work, are finally produced. As a necessary complement to the mostly theoretical and computational approach presented in this work, a series of four-point bending tests has been performed on reduced scale slabs placed in a furnace. The results of these tests partially validate the predicted interaction diagram of a fire loaded panel section

This diploma thesis deals with the design of a steel structure of a multi-storey building in the locality of Opava. The proposal is developed in two variant solutions. Variant 1 has ground plan dimensions of 37,5 m x 37,5 m and a height of 47 m. The variant 2 has ground plan dimensions of 45 m x 45 m and a height of 49,5 m. The modular size of the fields is 7,5 m x 7,5 m. The main supporting structure is made steel columns and beams, ceiling construction with composite steel and concrete joinst and roofing of arched laminated timber. The stability of the structure is ensured by vertical and roof bracings.

Diploma thesis deals with design of selected parts of reinforced concrete construction of a multi-storey building with respect of fire resistance. The proposed elements are reinforced concrete locally suported ceiling slab, selected column and wall. These structures are located in the storage hall on the 1st underground floor. Different variants of structural design are consulted and compared in this work. The calculation of internal forces is performed in the calculation software Scia Engineer 19.1. The thesis includes a structural design as well as drawings. The construction is designed according to ČSN EN standarts.

This master‘s thesis is focused on the study of the behavior of cement concrete at high temperatures with a focus on monitoring the impact of aggregate and cement type. This work describes the processes in aggregates and cement matrix at high temperatures. The theoretical part describes the selestion of a suitable aggregate and cement for the surroundings with potential exposure to high temperatures. In the experimental part is given design of composition of a concrete with two types of aggregates and four cements. It has been suggested 8 recipes. Changes were observed densities, compressive strength and tensile strength in bending, calculate the velocity of propagation of waves with ultrasonic pulsed method. Also evaluated the appearance of the surface samples after thermal load – cracks on the surface and measure the maximum crack width.

The thesis deals with composite systems, with a focus on matrix resistant to extreme conditions. The aim of this work was to research and development matrix, resistant to high temperatures, typical in case of fire. Used theoretical knowledge were realized with subsequent laboratory research. Attention was paid matrices based binder mixed with any alkali activation of alternative raw materials and geopolymers. Scattered reinforcement featured polypropylene fibers. The subject of the practical part of the two alternatives, including a matrix based on basic ingredients - cement, alternative raw materials - high fly ash, blast furnace slag, geopolymer and polymeric components incl. combinations thereof. Laboratory research conducted by determining the fundamental material properties such as density, strengths, etc., after heat exposure. The developed materials were subjected to a temperature 1400 ° C. The conclusion was selected several recipes that were based on the resulting values found to be optimal.

This final thesis is focused on a reinforcement design and check of selected reinforced concrete structure parts of a church building. A spatial model loaded with dead and live loads is designed in order to carry out a structural analysis in SCIA Engineer software. Serviceability limit state and fire resistance are then checked for some selected load-bearing elements. The drawings are also included in this work.